It is well known to provide adjustable lumbar supports in vehicle seats. Various different forms of adjustable lumbar supports exist and variation occurs both in the lumbar supports themselves and in the actuators that enable lumbar support adjustment.
Some manual actuators for lumbar supports include a rotatable knob which can be rotated both clockwise and anti-clockwise, in order to increase or decrease the extent of lumbar support. In some forms of this type of actuator, the mechanism of the actuator includes a braking function, to brake the actuator against backdriving from an adjusted position. The force applied to rotate the knob must be large enough both to overcome the braking load, as well as to perform the lumbar support adjustment. Because of this, the knob can be difficult to rotate. That difficulty can be accentuated as the knob is usually located in a confined position, such as on the side of the seat back, between the seat and the vehicle door frame.
Some lumbar support actuators are bulky, which can limit the seat designs with which they can be used. Also, many actuators require several revolutions of the knob to adjust the lumbar support between extreme positions.